This invention relates to a data recording and reproducing method and a data recording and reproducing apparatus.
With a shift to a multichannel used for the provision of information due to the wide spread use of a CATV (Cable Television) or the like, there has recently been an increasing demand that a plurality of video/audio data are simultaneously recorded into and reproduced from one video/audio data recording and reproducing apparatus and reproduced therefrom while recording the data therein, as distinct from a conventional VTR (Video Tape Recorder). In order to meet such a demand, an apparatus called a video server (or also called AV (Audio and/or Video) server) for recording and reproducing images and voice using non-linear accessible recording mediums such as a hard disk, etc. is becoming pervasive.
In general, a video server used in a broadcast station needs mass capacity to record long-time data in addition to an increase in the transfer rate of required data from a demand for the quality of an image and sound quality. Therefore, an attempt to speed up the transfer rate of data and make mass storage by using a data recording and reproducing apparatus including a plurality of hard disk (hereinafter called HD) devices capable of storing video and audio data therein and performing parallel processing, and an attempt to make it possible to ensure reliability by recording parity data in case of a failure in any of the HD devices have been made. Thus, a multichannel video server can be implemented which can cope with various usage forms, for example, the construction of systems such as VOD (Video On Demand), NVOD (Near Video On Demand), etc. by recording dispersively material data comprised of a plurality of audio and video data and performing the simultaneous transmission of data through the multichannel in this state even when the number of channels required according to the contents of programs offered from a broadcast station and broadcast forms vary, or by reproducing the same material data through the multichannel with staggered reproduction times.
In a data recording and reproducing apparatus employed in such a video server, an RAID (Redundant Arrays of Inexpensive Disks) technique for constructing a hard disk drive (hereinafter called HDD) comprised of a plurality of HD in plural form, which has been proposed by a paper (xe2x80x9cA Case for Redundant Arrays of Inexpensive Disks (RAID)xe2x80x9d, ACM SIGMOND Conference, Chicago, III, Jun. 1-3, 1988) published by Patterson et al. in 1988 has been used.
In the paper, RAID are classified into five levels ranging from RAID-1 to RAID-5. The RAID-1 level is a system for writing the same contents into two HDD. The RAID-3 level is a system for dividing input data into parts of a predetermined length and recording them on each of a plurality of HDD, and generating parity data corresponding to the exclusive OR of mutually-corresponding data blocks of the respective HDD and writing the parity data on another HDD. Further, the RAID-5 level is a system for increasing division units (blocks) of data, recording one divided data on one HDD as a data block, recording the results (parity data) of the exclusive OR of mutually-corresponding data blocks of respective HDD on other HDDs as parity blocks, and distributing the parity blocks to other HDDs. With respect to other levels of RAID, a reference is made to the above-described paper.
On the other hand, the video server is provided with an input/output processing processor for making it easy to store a material input from the outside in RAID referred to above, e.g., performing encoding/decoding such as compression, expansion or the like on it. When this one input/output processing processor treats with one input/output data (of one channel), the video server is provided with a plurality of input/output processing processors from the need of simultaneous execution of storage, transmission and editing and implements the input/output of a plurality of channels (multichannel).
Further, the simultaneous input/output of a plurality of channels is implemented by time-divisionally activating the input/output processors in assigned time slots. When, for example, one channel is used for data recording and four channels are used for data reproduction, one cycle, e.g., one second is first divided into five time slots ┌T1┘ through ┌T5┘ as shown in FIG. 11. During the time slot ┌T1┘, data corresponding to one channel is recorded and the recorded data is read out during the time slot ┌T2┘, whereby the data of one channel is reproduced and output. Further, the periods corresponding to the time slots ┌T3┘ through ┌T5┘ are also similar to the above, i.e., a process for reproducing and outputting data within the respective time slots ┌T3┘ through ┌T5┘ is performed. Thus, the recording of the data corresponding to one channel and the reproduction of the data of four channels can be simultaneously processed.
Meanwhile, such a data recording and reproducing apparatus has utilized two memories to record the data corresponding to one cycle in one time slot and output in one cycle the data read in one time slot. However, there may be cases in which if the timing provided to start operation upon data recording and reproduction is not adjusted, then the reading and writing of the data are simultaneously performed on one memory, whereby the operation thereof will fail.
When desired data is not read in a predetermined time slot where special reproduction such as fast-forward playback, fast-rewind playback or the like is performed by the video tape recorder, the special reproduction cannot be started, so that satisfactory response cannot be obtained.
Therefore, the present invention provides a data recording and reproducing method and a data recording and reproducing apparatus, which are capable of recording and reproducing data easily and properly and making response at a special reproducing operation satisfactory.
A data recording and reproducing method according to this invention, for recording input data on a non-linear accessible recording medium and reproducing the data recorded on the recording medium, using at least three data storing means, comprises a first step for writing the input data successively into the data storing means every predetermined units, supplying the written data to the recording medium through a transmission line on a time-shared basis, and recording the same on the recording medium, and a second step for writing the data read from the recording medium successively into the data storing means through the transmission line every predetermined units on a time-shared basis and outputting the data of predetermined units written into the data storing means.
Further, a data recording and reproducing apparatus according to this invention, for recording input data on a non-linear accessible recording medium and reproducing the data recorded on the non-linear accessible recording medium, comprises at least three data storing means supplied with the input data and for temporarily storing the input data therein, data recording and reproducing means for receiving the data output from the data storing means, recording the data on the non-linear accessible recording medium, reproducing the data recorded on the non-linear accessible recording medium and supplying the same to the storing means, time slot generating means for generating time slots, and control means for performing control for writing the input data successively into the data storing means every predetermined units, supplying the written data to the data recording and reproducing means within assigned time slots generated from the time slot generating means, and writing the data reproduced by the data recording and reproducing means successively into the data storing means within the assigned time slots generated from the time slot generating means.
In the present invention, recorded data are successively written into at least three data storing means every predetermined units upon recording the data therein. The data written into each data storing means is supplied to data recording means in an assigned predetermined time slot through a transmission line and recorded on a non-linear accessible recording medium. Here, the data corresponding to one cycle of assigned time slots, for example, is successively written into the respective data storing means.
On the other hand, when data is reproduced, the data corresponding to one cycle of time slots, for example, is read from the non-linear accessible recording medium and stored in the corresponding buffer. Further, the stored data is written into each of the data storing means in each assigned predetermined time slot through the transmission line. The data written into each data storing means is read with a time interval corresponding to one cycle of time slots and output as reproduction data.